Process of etching.



PA I'ENTED OCT. 4, 1904. T. 0. VAN Hons-mm WV MEYERS.

PROCESS-'0'?" ETGHING. APPLIOATION FILED JULY 24, 1903.

2' SHBETSSHEE,T If

no MIG-DEL.

Patented October 4, 1904.

UNITED STATES PATENT OFFICE.

THOMAS C. VAN HOUSEN AND WILLIAM AUGUSTUS MEYERS, OF CHICAGO, ILLINOIS.

PROCESS OF ETCHING.

SPECIFICATION forming part of Letters Patent No. 771,3 0, dated October 4, 1904..

Application filed July 24, 1903. Serial No. 166,854:- (No specimens.) l

Ton/Z7 whom it may concern:

Be it known that we, THOMAS C. VAN HOU- SEN and VVILLIAM AUGUSTUS MEYERs, both are to provide a process or method of subjecting the plate to the action of the liquid in such manner as to produce a more nearly uniform action upon the surface exposed; to provide a process in which the eroding liquid is impelled against the surface being acted upon and is so controlled in its circulation that it impinges against the surface in lines approximatch perpendicular to said surface, thereby rapidly deepening theindentations and minimizing the erosion of the relief portions inv lateral directions; to provide a process in which a carbon plate is arranged in proximity to the surface being etched and cooperates both by guiding the eroding liquid and by clarifying the same; to provide a process in which the plate being etched is made to form one element of a galvanic couple and a carbon grid the other element thereof and in such manner that electrolysis contributes to or accelerates the etching action; to provide a process which may be carried out in a simple and rapid manner and in such a way that inspection of the work may be had from time to time with greatest convenience, and in general to provide an improved process of the character referred to.

To the above ends the invention consists in the matters hereinafter described, and more particularly pointed out in the appended claims, and the invention will be readily understood from the following description, reference being had to the accompanyingdraw ings, illustrating a suitable apparatus for carrying out the process, and in which- Figure 1 is a plan view with certain parts.

in horizontal section of the apparatus.

but out of contact with the surface of the.

plate to be etched and arranged in parallel or approximately parallel relation to the latter. I also provide means for creating an agitation or circulation of the etchingfiuid, which means are arranged to impel the liquid through the grid or skeleton plate and against the plate to'be etched. Arranged in proximity to the surface to be etched the grid serves as a means of guiding the liquid and causing it to impinge directly against the surface of the plate and in lines approximately perpendicular thereto. By means of suitable agitating apparatus the flow of the liquid through the grid and-against the plate is made as uniform as possible over the entire surface to be etched, the liquid being so agitated as to avoid to the greatest practicable extent the creation of- K Fig. ,2 1s a longitudinal sectional view of the same,

promptly replaced by fresh solution. It will be understood, of course, that the plate being etched is first prepared in any of the wellknown ways by the application thereto in any pattern of a composition, such as dragonsblood, which protects fromthe action of the bath the pattern to be left in relief.

As a further adjunct of the process the skeleton grid referred to is made of carbon, which enables us to use the same as one element of a galvanic couple, and at the same time the porous character of the carbon, or perhaps some other peculiarity not fully understood, causes it to act as a clarifying agent in the bath. and plate being etched may act as a galvanic couple, these members are connected by one or 'more conductors, and we have found by practical demonstration that the current generated by the chemical action of the bath upon the plate augments the chemical reaction and renders the etching more rapid. We have further demonstrated that by employing an auxiliary and independent source of electricity the etching process is still further expedited, the electrical connections being so made that they cooperate with the current generated by the galvanic couple formed by the plate being etched and the carbon grid.

Describing now the apparatus illustrated in the drawings, Z designates as a whole a relatively shallow receptacle or tank made of suitable material to withstand the action of the bath and preferably open at its top. Nith- ,in'the lower part of said tank are journaled a plurality of agitator-shafts 2, arranged 'in the same horizontal plane, parallel with each other and at uniform distances apart. Upon each shaft is mounted a spirally-disposed agitator-blade 3, these blades being desirably mounted upon the shafts after the fashion of an ordinary conveyer shaft. The several shafts are revolubly mounted in the tank and operati vely connected, so as to rotate together. To this end each shaft is provided with an extension 4, which extends through a bushing 5, seated in a transverse partition member 6, the several bushings being provided with packing-glands 7 which surround the shaft extensions and prevent the escape of liquid from the tank. The shaft extensions4 extend through the end wall 8 of the tank and are provided upon their projecting ends with spur-gears 9, suitable journal-sleeves 10 being seated in said end wall, within which the shaft extensions are journaled. At their opposite ends the shafts 2 are mounted upon cone-bearings, and to this end a series of sleeves 11 are arranged to extend through the.

end wall 8 of the tank, within which sleeves are seated step-bearing screws 12, which terminate in a cone-point 13, which engages a corresponding bearing-recess formed inthe end of the corresponding shaft. The stepbearing screws h threaded engagement In order that the carbon grid with the interiors of the sleeves 11 and are also provided with packing-glands 14 to prevent the escape of liquid.

In order that the agitator-shafts may be removed bodilyfrom the tank, they are connected with their respective shaft extensions 4 by means of detachable couplings. These couplings each comprise a plate 15, provided at one side with a screw-threaded spur 16, which is engaged with a correspondingly-threaded socket in the end of the shaft extension and at its opposite side with a pair of studs 17 and 18, which engage corresponding sockets l9 and 20, formed in the end of the agitatorshaft, as shown clearly in Figs. 1, 4, and 5. By retracting the step-bearing screws the shafts are released, so that they may be dis connected from the coupling-studs 17 and 18 and lifted out of the tank.

The several spur-gears 9 ofthe agitatorshafts are arranged to intermesh with each otherpas shownclearly in Fig. 1, and with one of these, spur-gears is'connected a beltwheel 21, by means of which the shafts may be driven from any suitable source of power. 22 designates the plate which is to be etched, which is supported horizontally within the tank a short distance above and parallel with the series of agitator-shafts conveniently by means of wire loops or suspending-hooks 23, one end of each of which is hooked over the upper edge of the tank, while the lower'end extends beneath and supports the plate. In practice the tank is filled with etching solution to a point high enough to completely submerge the plate, as indicated by the waterline designated 24.

Immediately beneath the plate 22 and between the latter and the series of agitatingshafts is supported a carbon grid 25,.con'sisting in the present instance of a plate provided at regular intervals apart with openings 26. In the present apparatus said plate is shown as conveniently supported by means of a plurality of short supporting lugs or ledges 27, extending inwardly from the side walls of the tank.

In order that the grid 25 and plate 22, which is being etched, may act as a galvanic couple, these members are connected by one or more conductors 28, which are conveniently removable and attached to the plates by means of clamps 29$ These conductors will be of sulficient carrying capacity to reduce their resist ance to current to a very low degree.

' In addition to the conductors 28we have shown the two elements of the galvanic couple connected. in circuit with an exterior source of current, such source being indicated diagrammatically as a dynamo -in the present instance and the connections therewith indicated in dotted lines. When this auxiliary source of current is to be employed, the conductors 28 will be removed, so that the only metallic connection between the elements will be through the conductors 31 and 32, which serve also as leads connecting with the auxiliary source. It will be seen that these conductors 31 and 32 then serve not only to convey the current generated by the outside source, but also to convey such current as is generated by the electrochemical action of the galvanic couple and electrolyte. In this connection it may be noted that the auxiliary current may be used advantageously where it rent, since it will effect a more rapid action action.

of the acid by replacing the chemically-satisfied molecules with fresh acid.

The method as carried out by the use of the apparatus herein described will be entirely obvious and need not therefore be repeated. It is to be noted, however, that during the rotation of the agitator-shafts the liquid will be agitated very uniformly over the entire area of the tank, and by reason of the fact that the agitator-shafts alternately rotate in opposite directions a localized churning efiect will be produced, which will result in impelling the liquid away from the agitators, and since this churning efl'ect extends all over the area of the tank the liquid will be impelled away substantially at right angles to the plane of the agitators or in lines substantially normal to the face of the plate being acted 'upon. The open grid will serve also to guide the liquid to a certain extent, and more particularly to neutralize or prevent the formation of currents tending to sweep across the face of theplate in any direction. The result of the churning thus produced will therefore be to etch the plate uniformly and to deepen it rapidly, while the tendency to eat laterally into the relief portions will be minimized.

It is also to be particularly noted that the plate may be inspected from time to time with the greatest facility by simply lifting it out, reversing it, and examining the surface, the tank being open at its top and the supports so disposed that the plate may be lifted out without disturbing the supports.

The bath ordinarily employed for etching zinc is diluted nitric acid, and this acid acting on the zinc when electrically coupled with a carbon plate produces a galvanic couple having considerable electrical efficiency. The current thus generated, as hcreinbefore explained, contributes materially to the etching The amount of current thus generated is, however, very much less than the maximum amount which can be advantageously used, and accordingly we in some instances connect the galvanic couple with an auxiliary source of current supply, thus further accelerating the etching action.

The carbon grid, as hereinbefore mentioned,

acts in some manner to clarify the etching solution during the carrying out of the process. thus enabling the acid to be used 'efl'ectively for a longer period of time. Whether this clarifying action is due to the chemical precipitation or electrical deposit or is simply due to the filtering action of the more or less porous carbon grid has not as yet been determined; but this action is pronounced.

It will be understood that the method here-' in described is not by any means limited to the use of any particular etching solution nor to the etching of any particular model, it being obvious, on the contrary, that the process is applicable to etching generally. The apparatus herein shown is in itself novel and forms the subject of a separate invention the subject-matter of which is reserved for another application for patent.

We claim as our invention- 1. The improvement in the art of etching, which consists in supporting the article to be etched with the face to be acted upon submerged in an etching-bath and agitating the bath and at the same time impelling the liquid against the surface to be etched in directions substantially normal thereto, the agitation and impelling of the liquid being eflected at numerous localized points distributed uni formly over the area or opposite the surface to be acted upon, whereby sweeping currents. are prevented.

2. The improvement in the art of etching, which consists in supporting the article to be etched with the face thereof to be acted upon submerged in the etching-bath and churning the bath in proximity to, and opposite the.

said face, substantially uniformly over the.

'is impelled against said face.

3. The improvement in the art of etching, which consists in supporting the article to be etched with the face thereof to be acted upon submerged in the etching-bath, supporting a perforated grid opposite and in proximity to said face, and churning the liquid in proximity to the grid, whereby the liquid is impelled through the perforation of the latter and caused to impinge the face being etched, and sweeping currents across said face prevented.

4. The improvement in the art of etching, which consists in supporting the article to be etched with-the face thereof to be acted upon submerged in the etching-bath, supporting a perforated carbon grid opposite and in proximity, to said face, and churning the liquid in proximity to the grid, whereby the liquid is impelled through the perforation of ..t-he latter and caused to impinge the face being etched and sweeping currents across said face prevented.

5. The "iprovement in the art of etching 'which ex ,ists in electrically connecting the articl a be etched with another element of difiwent electrical potential to form a galvanic couple, applying to the article to be etched a composition protecting the covered parts from the action of the bath, supporting I the couple in a hath which is both an etching fluid and an electrolyte and at the same-time churning the bath in proximity to and opposite the face of the article being etched substantially uniformly over the entire area of the couple in a bath which is both an etching fluid and an electrolyte and also passing electric current from an external source through sic couple and electrolyte, and sily in'uielling the liquid against theezieng etched in directions substantially normal thereto, the agitation and impelling of the liquid being eii'ected at numerous localized points distributed uniformly over the area or opposite the surface being etched, whereby sweeping currents are prevented.

-7. The process ofetching metal articles which consists in applying to the article to be etched a composition protecting the covered parts from the action of the etching fluid, subjecting the article to the continuing action of an etching fluid which is both an etching fluid and an electrolyte, connecting the article being etched in an electric circuit which includes the electrolyte, whereby the electrochemical action induced by the electric current is auxiliary to the etching action, and simultaneously churning the bath at numerous points distributed uniformly over the area thereof, wherebysweeping current-s are-preented.

THOMAS C. VAN HOUSEN.

I WILLIAM AUGUSTUS MEYERS. Witnesses:

ALBERT H. GRAvEs,

FREDERICK (J. GoonWIN. 

